The present invention relates to a novel branched organopolysiloxane and to a method for its preparation. More specifically, the present invention relates to a novel branched organopolysiloxane, and to a method for its preparation, in which the central branch region or element (the branch origin) is a polysiloxane unit represented by the formula SiO.sub.2 and the branch moiety proper is a diorganopolysiloxane unit.
Numerous branched organopolysiloxanes have already been proposed and even commercialized. However, there are few reports relative to branched organopolysiloxane in which the central structure of the branch is a polysiloxane unit with the formula SiO.sub.2. Moreover, many of these branched organopolysiloxanes reported to date are no more than the product of simply mixing and reacting SiO.sub.2 component with diorganopolysiloxane component, and their structures are by no means clear. For example, the reaction of hydroxy-terminated polydimethylsiloxane and tetraethyl silicate by the sol-gel process to produce polymer has been reported (H. Huang, et al., Polymer Bulletin, Volume 14, pp. 557-564 (1985)). However, a clear structure was not reported for this polymer, and both ends of the diorganopolysiloxane in this polymer are bonded to branch points. To date, there have been no reports of a so-called "star organopolysiloxane" in which polysiloxane with the formula SiO.sub.2 constitutes the branch origin and only one side of the diorganopolysiloxane component is bonded to the branch origin wherein this bonding is exactly to the branch origin.